Dogs can be picky eater and especially when they are generally exerting little energy throughout the day, which doesn't help develop their appetite.
Most commonly however, dogs will eat during the evening because they've not been presented with accomplishment-related opportunities where they use both their brain and body to find, scavenge and enjoy getting each piece of their meal!
In short, make sure you provide ongoing opportunities for enrichment to build on your dog's appetite and they'll be more likely to want to eat throughout the day.